Split-Beam Array - Main Floor And Balcony - Community ENTASYS Application Manual

DESIGN APPLICATION EXAMPLES
S P L I T‐ B EA M A R RAY – M A I N F LO O R A N D BALCO NY
Design Approach
This design example features a house of worship with a high ceiling and a balcony at the rear of the room. It exhibits a mid-
band RT of 2 seconds, increasing to 3.5 - 4.0 seconds below 500 Hz. The sound system will be used for spoken word as well
as musical reproduction. Because of the long reverberation time in the lower frequency region, a large array will be employed
to help minimize reflections from the ceiling. Low frequency extension loudspeakers will be placed directly below the arrays
for better LF directivity down to 200 Hz. These will be used judiciously to avoid excessive reflections in this frequency region,
while providing more natural sounding reproduction of speech and music.
The main audience area is drawn in EASE Focus, with the array located on the front wall (Figure 40). This places the audience
area between 11 and 76 ft (3.4 - 23.2 m) from the loudspeaker position. To provide optimal coverage to both the main floor
and the rear balcony, a split-beam array is configured using two sets of two Full-Range modules, separated by a Low Frequency
module in the middle of each array. The arrays are positioned very high, at 20.5 ft (6.3 m), allowing the upper portion of the
array to cover the balcony while providing sufficient space below the array to locate the subwoofer.
The configuration and position of the array are transferred from EASE Focus to the EASE model. Since EASE Focus only
models in two dimensions, the azimuth (horizontal aiming angle) of the arrays must be adjusted in the EASE 3D model. The
arrays are aimed 15 degrees inwards to provide optimal coverage. Reference Page 54-55, regarding early reflections in the
front corners and their effect on the quality of sound.
Because of the large number of ENTASYS systems used, the system design specifies two separate amplifier channels for each
array. Powering the two upper-most loudspeaker modules from one channel and the three lower ones from another amplifier
channel will provide for a degree of independent level control over the modules covering the main floor and the balcony. This
may be useful for the final on-site adjustments during commissioning.
Results
The audience areas on the floor (Figure 41) exhibit fairly uniform direct SPL, ranging from 107 dB in the front corners near
the arrays to 102 dB at the back of the room underneath the balcony. The SPL in the balcony area is 101 - 102 dB. The
potential intelligibility of this system shows C50 at -3 dB (+/- 1 dB). The STI is approximately 0.52 and the %Alcons is about
10.5%. The intelligibility calculations are remarkably good given the reverberation time of the room.
What To Look Out For
The split-beam array should help to focus energy away from the balcony fascia. Depending on their composition and shape, the
balcony fascia and/or rear walls may exhibit some reflectivity issues, in which case absorption may be employed to minimize
these reflections.
Loudspeakers, Brackets, and Power Amplifiers Used in This Design
Two arrays, each configured from top-to-bottom as a Full-Range module (curved top), Full-Range module (curved bottom),
Low Frequency module, Full-Range module (curved top), and Full-Range module (curved bottom).
(2) ENTASYS Low Frequency Modules (ENT-LF)
(8) ENTASYS Full-Range Modules (ENT-FR)
(2) ENTASYS Pan Brackets (ENT-PB)
(8) ENTASYS Coupler Brackets (ENT-CB)
(2) VLF212 Subwoofers
(2) Two channel amplifiers rated at 3,600 W per channel into 4 ohms
(1) Two channel amplifier rated at 900 W per channel into 4 ohms
(1) Crossover with a high pass filter or DSP unit
Community ENTASYS Application Guide - Page 44